1. Field of the Invention
The present invention relates to a process and a device for calibrating a sampling and metering pipette and to a pipette permitting a completely automatic implementation of the process forming the subject of the invention.
2. Description of the Related Art
Sampling and metering pipettes which are available commercially at the present time, as shown in FIG. 1, comprise a pipette body 1 enabling the sample volume to be displayed. The sample volume is produced by a plunger 4 integrally fastened to a central rod 5, the plunger being movable in the pipette body 1 under the action of the central rod and the reaction of a return spring 6. An axial adjusting screw 2 meshes with the means 20 for displaying the sample volume, the adjusting screw being integrally fastened to a knurled button 3 permitting the stroke of the plunger in the pipette body to be adjusted. The central rod 5, and the plunger under the reaction of the return spring, comes normally into abutment on a positionally adjustable end-stop 7 at the end of the knurled button 3 in order to enable the zero setting of the stroke of the central rod 5 and of the plunger and, consequently, of the sample volume, to be adjusted.
For a more detailed description of a pipette such as described above, reference may usefully be made to French Patent Application No. 80/00,130, filed on Jan. 4, 1980 in the name of the same applicant and entitled DEVICE FOR SAMPLING AND DISPENSING ADJUSTABLE VOLUMES OF LIQUIDS WITH NUMERICAL DISPLAY.
To this day, this type of pipette has been wholly satisfactory both from the viewpoint of reliability in use and of the reproducibility of repetitive measurements or meterings.
However, before an apparatus of this kind is marketed, the unit needs to be calibrated, this calibration consisting, in effect, of a setting or adjustment of the zero of the sample volume.
Because of the actual structure of the system for setting or adjusting the zero of the sample volume, the above-mentioned calibration operations can only be successfully carried out by hand, obviously, and production of pipettes of this kind on an industrial scale involves, before they are launched on the market, the installation of a calibration station which is costly in manpower and in hardware, in order to ensure sufficient production. In addition, the essentially manual nature of the above-mentioned calibration operation cannot ensure a complete freedom from mistakes or faults in setting or in calibration, precisely because of the human factor, which is an unavoidable source of mistakes and of inaccuracy, a reduction in errors of this type requiring, for example, additional statistical control operations or the like.